Firing mechanism for a machinegun

ABSTRACT

A firing mechanism for a machinegun which comprises a bolt movable between a retracted and a battery position responsive to crank rotation and a firing pin slidingly disposed within the bolt. A firing pin spring is compressed by the crank-actuated drive pin during final displacement of the bolt to the battery position. Cam means rotates the bolt, when in battery position, around the firing pin into locked engagement with a barrel extension and thereby moves a recessed ramp in the firing pin into alignment with a sear fixed within the bolt bore for release of the firing pin when the locking engagement is completed.

bite States Patent Wohlford 1 Feb. 29, 1972 [54] FIRING MECHANISM FOR A 3,410,175 11/1968 Johnson et a1. ..s9/177 x MACHINEGUN 3,507,187 4/1970 Maillard ..89/l85 lnventor: William P. Wohlford, Davenport, Iowa The United States of America as represented by the Secretary of the Army Filed: Oct. 20, 1970 Appl. No.: 82,278

Assignee:

References Cited UNITED STATES PATENTS 2/1917 Brotherston ..89/1 1 8/1922 Fokker ..89/1l 3/1930 Hudson ..89/llXf Primary Examiner-Samuel W. Engle Attorney-Harry M. Saragovitz, Edward .1. Kelly, Herbert Berl and Albert E. Arnold, Jr.

A firing mechanism for a machinegun which comprises a bolt movable between a retracted and a battery position responsive to crank rotation and a firing pin slidingly disposed within the bolt. A firing pin spring is compressed by the crank-actuated drive pin during final displacement of the bolt to the battery position. Cam means rotates the bolt, when in battery position, around the firing pin into locked engagement with a barrel extension and thereby moves a recessed ramp in the firing pin into alignment with a sear fixed within the bolt bore for release of the firing pin when the locking engagement is completed.

ABSTRACT 5 Claims, 6 Drawing Figures FIRING MECHANISM FOR A MACHINEGUN The invention described herein may be manufactured, used and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION This invention relates to machineguns and pertains more particularly to the firing mechanism thereof.

One of the most bothersome problems which confront engineers in the field of machinegun design has to do with the sear which releasably holds the firing pin cocked against the force of a compressedspring and with the means for releasing the firing pin at exactly the right moment in the operating cycle. In many situations, design engineers have had to meet operating criteria in which relatively small and critically precise areas are, provided where the sears engage the firing pins and with intricate arrangements for actuating the sear to release the firing pins. Many such arrangements have been found difficult to control, are difi'icult to manufacture, and are prone to trouble.

SUMMARY OF THE INVENTION It is a principal object of this invention to provide for maehineguns having a longitudinally reciprocating bolt which carries a firing pin for longitudinal displacement therein a firing mechanism which is rugged and simple in construction without any relatively small and critical areas of contact between the firing pin and sear, in which the firing pin is positively secured in cocked position until the bolt is securely locked in the barrel extension, and which does not require an additional component for actuation of the sear to release the firing pin.

In accordance with the present invention, the operating means which reciprocates the bolt between a retracted and a battery position, is provided with cam means for rotating the bolt around the firing pin when the bolt is in battery position. The sear is of bar configuration and is fixed within the bolt bore so that the end of the sear contacts the front face of the firing pin body to securely block the firing pin in a cocked position. A ramp is located in the firing pin body so as to be aligned with the sear, for release of the firing pin, when rotation of the bolt to its locked engagement with the barrel extension is completed.

Further objects and advantages of the invention will become apparent from the following specification and the accompanying drawings which are for the purpose of illustration only.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinally cross-sectioned side view of the portions of a machinegun which embody the firing mechanism of this invention and shows the bolt actuated to where the locking lugs are engaged with the cam grooves in the barrel extension and the firing pin is seared in its cocked position;

FIG. 2 is a top view of a lateral cross section of the machinegun shown in FIG. 1;

FIG. 3 is a fragmentary, longitudinally cross-sectioned view, similar to FIG. 1, showing the bolt in its retracted position;

FIG. 4 is a view similar to FIG. 3 but shows the relationship of the gun parts when the locking lugs on the bolt have moved through the cam grooves in the barrel extension during forward movement of the bolt;

FIG. 5 is a view similar to FIGS. 3 and 4 but shows the relationship of the gun parts with the bolt in its locked battery DESCRIPTION OF A PREFERRED EMBODIMENT Shown in the drawings are portions of a machinegun 12 comprising a receiver 14, with a feed port 15, and a barrel 16, with a barrel extension 18 extending rearwardly therefrom. A cylindrical bolt 20 is slidingly disposed in receiver 14 for longitudinal displacement between a rearward retracted position and a forward battery position, to transfer a cartridge 21 from feed port 15 into barrel 16, and for rotational displacement between an unlocked position and a locked position to secure the breech end of the barrel during discharge of the chambered cartridge. A pair of locking lugs 22 extend oppositely and diametrically from the front end of bolt 20 for engagement with locking structure in barrel extension I8 when the bolt is in battery position and rotated to the locked position as hereinafter described. Locking lugs 22 slidingly engage channels 28 longitudinally formed inside of receiver 14 to prevent rotational displacement of the bolt until engaged with the locking structure in barrel extensions 18 as hereinafter described. An axial bore 30 extends forwardly into bolt 20 from the rear end thereof to a wall 32 for slidingly receiving a firing pin 34 for longitudinal displacement between a forward striking position and a rearward retracted position. Firing pin 34 comprises a cylindrical body portion 36 and a striking pin 38 which extends axially from front face 40 thereof. Striking pin 38 is slidingly received by an orifice 42 extending coaxially from bore 30 through wall 32 and is arranged to project from front end 44 of bolt 20, when firing pin 34 is in its striking position, to discharge the chambered cartridge 21, as shown in FIG. 5. A cylindrical hole 46 extends forwardly from the rear end of body portion 36 to a bottom surface 48 for receiving a coiled compression spring 50 the front end of which bears thereagainst.

Bolt 20 is reciprocated between the battery and retracted positions by any known driving means such as a crank 52 having a crankpin 53 which is connected by link 54 to a drive pin 56. Such drive pin 56 extends laterally through bolt 20 by means of a pair of oppositely disposed cam slots 58 therein and also through body portion 36 by means of a pair of oppositely disposed longitudinal slots 60 respectively provided with a rear end 61. Drive pin 56 is engaged by the rear end of spring 50, through a pad 62, for biasing firing pin 34 forwardly to the striking position. The ends of drive pin 56 extend from opposite sides of bolt 20 and mounted on each of such extending ends is a roller 64 which engages one of the channels 28. Vertically disposed finlike extensions 68 from the rear portion of receiver 14 provide space for rotation of crank 52 and oscillation of link 54. Vertical slots 70 and 72 are formed, respectively, in the rear ends of bolt 20 and firing pin 34 to provide clearances for the oscillation of link 54 relative thereto.

Barrel extension 18 is provided with an axial bore 74 which receives the front end of bolt 20 when moving into battery position and which is counterbored at 76 so that when the barrel extension is assembled as by thread means to the breech end of barrel 16 an annular chamber 78 with a locking surface 80 is formed rearwardly of the barrel breech to receive locking lugs 22 when the bolt is rotated to the locked position. Carn grooves 82, located in barrel extension 18 in alignment with channels 28, receive locking lugs 22 when bolt 20 goes into battery position and such cam grooves are angularly formed so that when the locking lugs pass therethrough into chamber 78, as shown in FIG. 4, the bolt is rotatable in a clockwise direction, looking from the rear end of machinegun 12 to the front end thereof.

Bolt cam slots 58 include a right cam slot 86 and a left cam slot 88 which are of dogleg configuration and they, respectively, include pockets 90 and 92 disposed diametrically apart in a lateral plane so that when drive pin 56 is seated therein locking lugs 22 are aligned for entry into extension cam grooves 82 as bolt 20 goes into battery position. Right cam slot 86 comprises an angular section 94 which extends forwardly and in a counterclockwise direction from pocket 90 and which leads to a longitudinal section 96, while left cam slot 88 comprises an angular section 98 which extends similarly frorn pocket 592 to a longitudinal section 100. Thus, when drive pin 56 is moved from pockets 01) and 92 along angular sections 94 and 98, bolt 20 is rotated clockwise to its locked position and as the drive pin continues along longitudinal sections 96 and 100, the bolt is secured against rotation from its locked position.

As drive pin 56 is moved along cam slots 58 it also moves along longitudinal slots 60 in firing pin 34 against pad 62 to compress spring 50 with firing pin 34 being held in a cocked position forwardly of its retracted position by a sear 102. Sear 102, of resiliently deflectable bar configuration, is longitudinally disposed rearwardly in bore 30 of bolt 20 and is fixed thereto by engagement within a recess 104 which extends forwardly from wall 32 at the circumference of the bore. The rear end of sear 102 is provided with a toe portion 106 which extends inwardly therefrom for contact by front face 40 of firing pin 34 when bolt 20 is in the unlocked position to releasably secure the firing pin in the cocked position, as shown in FIGS. 1 and 2. A recessed, longitudinally disposed rarnp 108 extends rearwardly and outwardly from front face 40 of body portion 36 to outside surface 109 thereof and is located so as to be aligned with sear 102, for engagement thereby, when bolt 20 is in its locked position. A channel recess 110 is formed in the cylindrical wall of bore 30 in back of sear 102 to permit deflection thereof when resiliently displaced by camming contact of ramp 100 with toe portion 106 during movement of firing pin 34 to its striking position.

OPERATION The operating cycle of machinegun l2 commences when crank 52 is rotated to where crankpin 53 is in its rearrnost position, with link 54 in longitudinal alignment with bolt 20, the bolt is in its retracted position, with drive pin 56 seated in pockets 90 and 92, as shown in FIG. 3, and firing pin 34 is held cocked by sear 102. As crank 52 continues its rotation in a clockwise direction, drive pin 56 is moved forwardly with rollers 64' thereon moving along channels 28. Because of the sliding engagement of locking lugs 22 with channels 28 bolt 20 is restrained from rotation. Thus, drive pin 56 is retained in pockets 90 and 92 and thereby the forward displacement of the drive pin is transferred to the bolt 20 which is driven forwardly from its retracted position to move cartridge 21 from feed port into the chamber of barrel 16 for discharge.

When bolt approaches battery position, as shown in FIGS. 1 and 2, locking lugs 22 move from channels 28 through cam grooves 82 thereby causing the bolt to rotate. This rotation of bolt 20 moves angular sections 94 and 08 into engagement with drive pin 56 thereby continuing the rotation of the bolt, during the continued forward travel of the driving pin, to where locking lugs 22 are located in chamber 78, as shown in FIG. 5, forwardly of locking surface 80 to secure the bolt against rearward displacement when cartridge 21 is discharged.

While drive pin 56 is moved along cam slots 58 it acts against pad 62 to compress spring 50, as firing pin 34 is held against displacement relative to bolt 20 through the contact of sear 102 with front face 40 of body portion 36 of the firing pin. However, bolt 20 is rotated around firing pin 34 to move ramp 108 thereon towards alignment with sear 102. When rotation of bolt 20 to the locked position is completed, ramp 108 is in alignment with sear 102, whereby firing pin 34 is released therefrom and is propelled forwardly by compressed spring 50 to its striking position in impact against the chambered cartridge 21 for discharge thereof. After bolt 20 is locked and firing pin 34 is released for discharge of cartridge 21, drive pin 56 is moved forwardly and then rearwardly by crank 52 along longitudinal sections 96 and 100 to provide sufficient time for the gas pressure generated by the discharge to be reduced to safe limits in barrel 16 before bolt 20 is unlocked therefrom.

When firing pin 34 was propelled by spring 50 to its striking position, sear toe portion 106 was deflected radially outwardly by ramp 108 to finally rest on outside surface 109, as shown in H0. 6. During the second half of the rotating cycle of crank 52 the rearward movement of drive pin 56 along longitudinal sections 96 and 100 and against rear ends 61 of longitudinal slots 60 in firing pin 34 moves the firing pin to its retracted position, with the portion 106 moving down ramp 108 back to its normal position clear of front face 40. When drive pin 56 engages angular sections 94 and 98 bolt 20 is rotated so that sear 102 is out of alignment with ramp 108. At the completion of one revolution of crank 52 bolt 20 and firing pin 34 are returned to their original positions as described for the commencement of the operating cycle.

I wish it to be understood that 1 do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

I claim:

1. A machinegun comprising a barrel with a barrel extension mounted to the breech end thereof, movement producing drive means, a bolt disposed for longitudinal reciprocation between a retracted and a battery position responsive to movement of said drive means, a firing pin provided with a front face disposed in an axial bore in said bolt for longitudinal displacement therein between a retracted and striking position, spring means for biasing said firing pin to the striking position, means for converting movement of said drive means to rotation of said bolt, when in the battery position, relative to said firing pin for locked engagement thereof with said barrel extension, a scar mounted to said bolt within said bore for contact with said front face of said firing pin to block movement of said firing pin from the retracted position thereof, and means in said firing pin disposed in cooperation with said sear for releasing said firing pin to the striking position when said bolt is fully rotated into locked engagement with said barrel extension.

2. The machinegun as defined in claim 1 wherein said bore is terminated by an end wall, said sear is of a bar configuration and is resiliently deflectable and comprises one end retained by a recess extending forwardly from said end wall for rearward extension of said sear therealong and a toe portion extending inwardly from the opposite end of said sear for blocking contact with said front face, and including a recess in the cylindrical surface defining said bore for receiving said sear when deflected away from contact with said front face.

3. The machine gun as defined in claim 2 wherein said firing pin includes a cylindrical body portion and a striking pin extending coaxially from said front face thereof, and said means in said firing pin comprises a recessed ramp extending rearwardly and outwardly from said front face to the outside of said body portion for receiving said toe portion when said bolt is rotated into full locket engagement with said barrel extension and for resiliently deflecting said sear into said channel when said firing pin thereby released is impelled by said spring means to the striking position.

4. The machine gun as defined in claim 3 and including a receiver for slidingly mounting said bolt, a drive pin extending through said bolt and said firing pin, a roller mounted on each end of said drive pin for engagement with longitudinal channels formed within said receiver to guide said drive pin for longitudinal, translational displacement therein, a link connecting said drive pin to said drive means for reciprocally moving said drive pin along said channels responsive to movement of said drive means, a pair of longitudinal channels formed in said firing pin for receiving said drive pin for cooperation therewith to permit limited longitudinal and nonrotating displacement of said firing pin relative thereto, a pair of cam slots disposed in said bolt for receiving said drive pin and formed to cooperate therewith for rotating said bolt around said firing pin between a locked position and an unlocked position responsive to movement of said drive pin along said cam slots when said bolt is free for rotational displacement, a pair of locking lugs extending diametrically from the front end of said locking surface in said barrel extension during continued forward movement of said drive pin along said cam slots.

5. The invention as defined in claim 4 wherein said spring means comprises a coiled compression spring disposed between said firing pin and said drive pin for compression thereby responsive to forward displacement of said drive pin along said cam slots when rotating said bolt to the locked position thereof. 

1. A machinegun comprising a barrel with a barrel extension mounted to the breech end thereof, movement producing drive means, a bolt disposed for longitudinal reciprocation between a retracted and a battery position responsive to movement of said drive means, a firing pin provided with a front face disposed in an axial bore in said bolt for longitudinal displacement therein between a retracted and striking position, spring means for biasing said firing pin to the striking position, means for converting movement of said drive means to rotation of said bolt, when in the battery position, relative to said firing pin for locked engagement thereof with said barrel extension, a sear mounted to said bolt within said bore for contact with said front face of said firing pin to block movement of said firing pin from the retracted position thereof, and means in said firing pin disposed in cooperation with said sear for releasing said firing pin to the striking position when said bolt is fully rotated into locked engagement with said barrel extension.
 2. The machinegun as defined in claim 1 wherein said bore is terminated by an end wall, said sear is of a bar configuration and is resiliently deflectable and comprises one end retained by a recess extending forwardly from said end wall for rearward extension of said sear therealong and a toe portion extending inwardly from the opposite end of said sear for blocking contact with said front face, and including a recess in the cylindrical surface defining said bore for receiving said sear when deflected away from contact with said front face.
 3. The machine gun as defined in clAim 2 wherein said firing pin includes a cylindrical body portion and a striking pin extending coaxially from said front face thereof, and said means in said firing pin comprises a recessed ramp extending rearwardly and outwardly from said front face to the outside of said body portion for receiving said toe portion when said bolt is rotated into full locket engagement with said barrel extension and for resiliently deflecting said sear into said channel when said firing pin thereby released is impelled by said spring means to the striking position.
 4. The machine gun as defined in claim 3 and including a receiver for slidingly mounting said bolt, a drive pin extending through said bolt and said firing pin, a roller mounted on each end of said drive pin for engagement with longitudinal channels formed within said receiver to guide said drive pin for longitudinal, translational displacement therein, a link connecting said drive pin to said drive means for reciprocally moving said drive pin along said channels responsive to movement of said drive means, a pair of longitudinal channels formed in said firing pin for receiving said drive pin for cooperation therewith to permit limited longitudinal and nonrotating displacement of said firing pin relative thereto, a pair of cam slots disposed in said bolt for receiving said drive pin and formed to cooperate therewith for rotating said bolt around said firing pin between a locked position and an unlocked position responsive to movement of said drive pin along said cam slots when said bolt is free for rotational displacement, a pair of locking lugs extending diametrically from the front end of said bolt for sliding engagement within said receiver channels to prevent rotation of said bolt relative to said firing pin and to retain said drive pin in the rear ends of said cam slots for transferring forward displacement of said drive pin to said bolt, cam grooves formed in said barrel extension for receiving said locking lugs from said channels when said bolt approaches battery position to initiate rotation of said bolt and movement of said drive pin along said cam slots to thereby effect rotation of said bolt to the locked position in engagement with a locking surface in said barrel extension during continued forward movement of said drive pin along said cam slots.
 5. The invention as defined in claim 4 wherein said spring means comprises a coiled compression spring disposed between said firing pin and said drive pin for compression thereby responsive to forward displacement of said drive pin along said cam slots when rotating said bolt to the locked position thereof. 